Lightning arrester



NOV- 23, 1948- w. c. HAssELHoRN Erm. 2,454,448

LIGHTNING ARRESTER Filed Aug. 22, 1345 Patented Nov. 23, 1948 LIGHTNINGARRES TER Walter C. Hasselhorn and John F. Jaap, Chicago,

Ill., assignors to Cook Electric Company, Chicago, Ill., a corporationof Illinois Application August 22, 1945, Serial No. .612,098

6 ClaimS.

This invention relates to lightning arresters or dischargers fortelephone lines and the like, to protect the lines and instrumentstherein from high voltage currents due to lightning or other causes.

The ordinary arrester of this type, as is well known, comprises twosmall carbon blocks usually separated by a thin dielectric which as aunit is slipped between holding contact springs or supports connected toor in the circuit to be protected.

Such arresters are intended to have fixed spark gaps to give the desiredprotection, but due to manufacturing difficulties do not always do so.Also, in such arresters the carbons are exposed on their exterior facesand tend to absorb moisture, which lowers their resistance, affectstheir capacity and causes them to deteriorate. They are exposed more orless to dust, dirt and moisture on their discharging surfaces.

It is an object of this invention to provide an arrester or dischargerwhich shall overcome the objections noted and possess advantages of itsown; in which the air gap may be accurately adjusted under test for anydesired fixed voltage and will remain so set indefinitely in use; inwhich the spark gap of the electrodes is enclosed in a chamber which issealed and kept free from dust, dirt and moisture; in which the exposedsurfaces of the carbon electrode are protected from moisture; and whichis economical of manufacture, eiiicient in use, of long life, andpossesses many other advantages, as will appear.

In carrying out the invention, an insulating body of thermoplasticmaterial, which may be transparent, is molded of the desired form,preferably if for telephone or like use, to be slipped into pla-cebetween the holding contact springs or supports of the circuit to beprotected, in place of the usual carbon-block arrester assembly referredto. A carbon block forming one of the electrodes is preferably molded inone side of the body with its outer moisture-proofed face exposed forengagement with the holding contact spring or support on that side ofthe body.

This latter feature-the molding of the carbon electrode in theinsulating body--is important andan object of the invention, since itprovides a means of including a moisture-proof carbon electrode with itsexposed spark gap or discharging surface in a hermetically sealedmoistureproof chamber, strongly and accurately holds the same thereinwithout attaching screws or other mechanical means to hold the electrodein the insulating body or in the device as a whole, and

lends itself to accurate manufacture by simple production methods.

The other opposed electrode of suitable metal preferably is adjustable,as by being threaded into the molded body, whereby the same may beaccurately set for the desired spark gap as determined by -test andinstruments at the manufacturing plant, the sparking being observable bysight through the insulating body if the same is transparent and thespark gap setting thus determined or checked.

After the setting of the spark gap, the threaded connection of theadjustable electrode with the insulating body may be further sealedagainst the entrance of moisture to the spark chamber by ap plying asuitable sealing cement thereto.

Suitable connection is made with this adjustable electrode for contactwith one of the circuit contact springs or supports. when the body isslipped into position, like other arrester units between the circuitcontact springs or supports, the outer face of the carbon electrode onthe opposite side of the body contacting with the other circuit springor support, the result being a moisture-proof, hermetically sealedspark-gap chamber arrester unit Which cannot change its rating ordeteriorate `in use or in handling, but in which the spark gap may beadjusted when desired for different voltages.

Further objects and advantages will appear from the description andclaims to follow, in connection with the accompanying drawing, whichillustrates, by way of example, but not of limitation, an embodiment ofthe invention, and in which- Fig. 1 shows an ordinary installation wherethe arrester may be used;

Fig. 2 is a face View on an enlarged scale of the complete device,looking at the side with the adjustable electrode;

Fig. 3 is a longitudinal central section of the same through theelectrodes and taken on the line 3 3 of Fig. 2; and

Fig. 4 is a central cross-section of the device,

' also through the electrodes, and taken on the line 4--4 of Fig. 3.

Referring to the drawing, Fig. 1 indicates a typical telephoneinstallation or the like where the arrester of this invention,designated generally by the numeral I0, may be employed in the wellknown manner in place of the usual carbon block arrester. In sucharresters, usually a supporting spring contact Il presses against oneside of the arrester body and besides making electric Contact therewithpresses the arrester as a unit against a contact support l2 on the otherside of the arrester, which makes electric contact with the otherelectrode of the device.

The arrester or discharger here shown comprises an insulating body orblock 2li of molded thermoplastic material which will shrink on cooling,is preferably devoid of cold ow and may be transparent, the materialknown as polystyrene being found satisfactory for the purpose.

Molded in one side of this body or block is a at carbon block 2| to formone electrode oi the discharger or arrester. By being molded in theinsulating block, the carbon block, which may be rectangular in form, istightly and firmly held therein and continues to be so held in the useof the device, to-wit, in a nXed or immovable relation due to thegripping action oi the thermoplastic material upon cooling during themolding operation, and, also, due to the substantial absence of coldflow of the thermoplastic material when thermoplastic material of sucha, Characteristic is used. The outer face of the carbon block extendsoutside and beyond the outer face oi the insulating block to make goodelectrical contact with the support l2 and spring il when `inserted in aholder for use.

This carbon block or electrode 2| maybe moisture-proofed, preferably bycoating its entire survface, with a silver conductive coating 22 which'is moisture and weather-proof and electrically conductive, and which maybe applied as a coating to the carbon block by dipping, spraying orplating, Before molding the coated electrode in the insulating block, asuitable area on the inside face ythereof that will oppose the otherelectrode I in the completed arrester is spot-faced by a suitable toolor tools to remove the coating and leave the carbon surface in cleanedactive condition for proper operation as an arrester or discharger.

'In the opposite side of the molded block 2O from `the carbon electrodethere is molded a threaded aperture 25 to receive a correspondinglythreaded metallic electrode 26, said electrode itting tightly thereinand having wrench sockets 2l in its cuter end or other means provided toenable the same -to be threaded into said aperture 255 and to beaccurately and firmly adjusted therein with respect to the opposingcarbon electrodeand, when finally adjusted, to resist the turning effectof th'e contact screw, yet to be described.

While this threaded connection of the metal electrode '26 with themolded body 20 may be substantially moisture-tight, it is preferred,after the electrode is finally adjusted, .to t a ring 23 of suitablemoisture-proof wax or cement about yand into the circumferential cornerbetween the outer end of the electrode andthe threads of aperture 25,which positively prevents the entrance of moisture by `way of thethreaded connection to the hermetically sealed chamber l5 that is thusprovided, At the same time, the electrode 26 is not anchored so rmlythat it may not be turned for adjustment purposes when desired. Due tothe high vaporizing point of tungsten, it is desirable *to use the sameat the gap by welding a tungsten contact lil to `the body of theelectrode 26, which body'portion may comprise any suitable material as abacking for the 4tungsten contact b, such as steel or Everdur 'In orderproperly and conveniently to connect the electrode 26 in the circuit andwith the holding spring or its equivalent, the electrode mal7 have acentral threaded recess into whicha lscrew 30 threads, said screwpassing through a lcontact plate or strip 3| rand having a bevelled headl3.2

adapted to lit into a corresponding depression 33 in the strip 3| andhaving a turning slot 34 therein. The strip 3|, having the outline shownin Fig. 2, nts snugly into a corresponding depression molded in the faceof the insulating body 20 and is curved longitudinally, as indicated inFig. 3, to conform to the curved face of the body, with its depression.33 entering the aring opening of the threaded aperture 25 in the bodyfor the electrode 23. The contact strip 3| lies in and transverselyspans the space between the raised ribs 35 along the longitudinal edgesof the body 23, which serve as guide and positioning ribs of thearrester unit on the spring Il or other support for the arrester in thecircuit to be protected. The slightly raised or deeper ends 36 of theribs 35 are for ease in handling the unit and enabling it to be readilygrasped for pulling it out or its supports.

The screw 3|), when tightened, electrically connectsthis Acontact strip3l with the electrode 26 by a positive connection. The circuit contactspring Il, which may be suitably curved endwise, makes electricconnection with the spring strip 3| and the head 32 of screw 30, andthrough the latter with the electrode 26.

The ribs 35 along the longitudinal edges of the insulating body may .berecessed slightly, as at 3l in Fig. 2, to accommodate the outward flareof the -threaded opening `25 in the body, the depression 33 in thecontact strip 3| and the head 3,2 of the screw 35). The spring strip 3|may be sprung or bowed out normally from its position when nally securedin place and a tight fit produced end-wise in the depression for it inthe body, so that, when the screw 30 is tightened, the strip will betightly iitted into position, as indicated in liig. 3, against the body.

The spark gapfof the'arrester., which is between the central part of thecarbon electrode 2| and the inner end of the metal `electrode 2B, `thelatter being preferably cut away `a little at the 'circumlerentialcorner 29, is thus provided Iin moisture-proofhermetically-sealed.chamber I5. The gap may be adjusted by screwing theelect-rode 23 in or out more or less to cause the discharge thereacrossor sparking to take place at the desired voltage, suitable testingapparatus at the pla-nt being available for such purpose. If transparentmaterial be used for the body, the spa-rking becomes visibletherethrough' and the same may be used to .determine the desired lengthof spark gap or to check the same without disturbing the hermeticallysealed chamber I5.

When the gap has been determined and sealing wax 'or cement 23 applied,the strip 3| is applied and the screw 33 inserted and. tightened. Thearrester is then ready for use.

If it be desired to readjust the arrester for a different voltage, screw3B and strip 3| are removed, and by a suitable too-1 or wrench theelectrode 26 is turned, the seal 23 being broken thereby, and th'e gapis readjusted accordingly. When done, the parts are restored to their:former condition andthe arrester isread-y for use at the new rating.

The adjustment by means of the threaded electrode enables the spark gapto be accurately and firmly adjusted in a vmost convenient and effective`manner and saves the disagreeable and difcult job of grinding off ythecarbon surfaces in a cut-and-try method.

The structure uniquely provides a hermeti- Ically sealed spark `gap'chamber that may be cleansed of dirt andmoisture ybefore beingsealed.

Providing a conductivecoating on carbon electrode 2| renders theelectrode impervious to moisture and prevents any seepage of moistureinto chamber l5. Moreover, it prevents undesirable fungus growth or theentrance of other foreign matter that is apt to aiect the operation ofthe device. Embedding electrode 2| in block during the molding operationassures a permanent and an accurate positioning of the electrode whicheliminates the inaccuracies resulting from manufacturing. The inner facewill always be in a plane parallel to the inner face 40 of electrode 26and a hermetical seal secured between body 20 and electrode 26. It willbe remembered that thermoplastic material, such as an artificial orsynthetic resinous lcompo-und or other thermoplastics, will contractupon cooling so that electrode 2| will be firmly held by the moleculartension of the material and a very effective hermetical seal providedthat will prevent seepage of moisture into chamber l5 between body 20and electrode 2|. On the other hand, fungus growth in chamber l5 or theentrance thereinto of any foreign matter will be effectively preventedwhich will allow unlimited use as to the location of the installa-tion.

We have found that once an adjustment of the spark gap is made, furtheradjustment is not necessary as a general rule, and hence, sealing at 28may be permanent. 1f an adjustment is desirable, the seal at 28 will notnecessarily be broken to the extent of destroying the hermetical seal ofchamber I5, and, if it is broken at all, the time required to make thechange and reseal is not suiicient to permit leakage past the threads ofelectrode 26. Another novel feature resides in the fact that screw 32may be removed to change strip 3| if required at any time withouteffecting lthe seal 28 or disturbing the spark gap adjustment. Arrestersof the type disclosed are used in many places. By providing body 20 oftransparent thermoplastic material, many advantages will be obtained.Body 20 will not be subjected to ready breakage and will stand roughusage without fracturing. The material will have eX- cellent insulatingqualities and is not permeable to moisture or gas. Hence, the arrestermay be used in places exposed to inclement weather conditions withoutbreaking down. Moreover, with a material of this type, the advantage ofbeing able to note readily the discharging across the gap through thetransparent body will ypermit locating quickly the circuit that isaffected and a quick repair of the lines.

Without further elaboration, the foregoing will so fully explain thegist of our invention that others may, by applying current knowledge,readily adapt the same for use under varying conditions of service,without eliminating certain features, which may properly be said toconstitute the essential items of novel-ty involved, which items areintended to be defined and secured to us by the following claims.

We claim:

1. A lightning arrester unit comprising an elongated molded body ofinsulating material, an elongated carbon block embedded and molded inone side of said body, said block having its outer face exposed forengagement with a circuit contact terminal, said block being coated witha moisture proof material except for the spark gap area on its innerface, a metal electrode threaded into said body opposed to said carbon.block and having its inner end in adjustable spark gap relationtherewith, means for rendering said heretofore threaded connectionmoisture proof, said metal electrode having a threaded hole thereinopening exteriorly, a metal contact strip overlying said metal electrodeon the outside of said body for engaging a circuit contact terminal, anda securing screw inserted through said Contact strip and into saidthreaded hole to mechanically secure the strip, body and electrodetogether and to electrically connect the strip and electrode, said bodyand electrode forming a closed and sealed spark gap chamber for thearrester.

2. A lightning arrester unit comprising a molded body of insulatingmaterial, a relatively` thin iiat carbon block embedded and moldedflatwise in one side of said body and permanently, tightly and rigidlyretained therein by the grip thereon of the material of the body inshrinking including that around the peripheral edge of 'the block, theouter face of said carbon block being exposed for engagement with a-circuit contact terminal and thc inner face thereof Within the bodyforming one of the opposed discharge surfaces of the spark gap of thearrester, said body having an aperture opposite said discharge surfaceof said block, an electrode positioned in said aperture, the spacebetween the said block and electrode enclosed by the adjacent wall ofsaid aperture forming a tightly closed spark chamber, and connectingmeans from said electrode to the outside of the body for engagement withanother circuit contact terminal.

3. A lightning arrester unit comprising a molded body of insulatingmaterial, a relatively thin ilat carbon block embedded and moldediiatwise in one side of said body and permanently, tightly and rigidlyretained therein by the grip thereon of the material of the body inshrinking including that around the peripheral edge of the block, theouter face of said carbon block being exposed for engagement with acircuit contact terminal and the inner face thereof within the bodyforming one of the opposed discharge surfaces of the spark gap of thearrester, said block being coated over the entire surface except for thespark gap area on its inner face with a moistureproofelectrically-conductive coating, said body having an aperture oppositesaid discharge surface of said block, an electrode in said aperture inmoisture-proof relation to the body, and connecting means from saidelectrode to the outside of the body for engagement with another circuitcontact terminal.

4. A lightning arrester unit comprising a molded body of transparentinsulating material, a relatively thin fiat carbon block embedded andmolded iiatwise in one side of said body and permanently, tightly andrigidly retained therein by the grip thereon of the material of the bodyin shrinking including that around the peripheral edge of the block, theouter face of said carbon block being exposed for engagement with acircuit contact terminal and the inner face thereof within the bodyforming one of the opposed discharge surfaces of the spark gap of thearrester, said body having an aperture opposite said discharge surfaceof said block, an electrode located in said apertiue, said transparentbody enabling observation of the sparking during such adjustment andthereafter Without opening the spark gap chamber, and connecting meansfrom said electrode to the outside of the body for engagement withanother circuit contact terminal.

5. A lightning arrester unit comprising a molded insulating body, acarbon block embedded in one side of the body, the outer face of theblock being exposed for Iengagement with a circuit terminal and ltheinner face having a spark gap discharge surface kthereon within thebody, an electrodein an aperture in the body having a discharge surfacein opposed spark gap relation to the discharge surface of said carbonblock, a contact strip on the outside of the bodyffor engagement Withanother circuit terminal and having a depression extending into saidaperture over the said electrode, and a screw connecting said strip withthe said .electrode and to said body, the headofxthe screwbeing seatedwhollywithin said depression.

V6. A lightning arrester unit comprising a moldedinsuiating body, acarbon block embedded in one side ofthe body-the outer face of the blockbeing exposed for engagement with a circuit terminal and the inner facehaving a spark gap discharge surface thereon Within the body, said bodyhaving an opening therethrough opposed 2 to said discharge surface onthe carbon block, a metallic electrode adjustably secured to said bodyin said opening Vand having a discharge surface in spark gap relationwith that on the carbon block, a Contact strip for the arrester on theout 25 side of said body 'having a conical depression extending andtting into the said opening in the body over the electrode, and a screwpassing through-thevbottomci -saidf depression andzthreading into saidelectrode, the 4head of [the screw'fitting and being seated Whollywithin the said depression, vwhereby -the head of the fscrew, thedepression .and opening may be secured together in vnested relation -tohold the said contact'strip in position on vthe body Without obstructionon theouter face of thecontact strip :andpto'electrica1ly.connec,tit=with the said electrodefandwithout disturbing the adjustment of saidelectrode in .the'body WALTER C. HASSELI-IORN.

.JOHN F. JAAP.

4REFERENCES CITED The following references are of record in the le of,this patent:

UNITED STATES PATENTS Number Name :Date

1,670,040 McCabe May 15, 19,28 1,901,893 Brodie Mar. 21, l1933`1,969,992 Rovere t Aug. 14, y193,4:

FOREIGN PATENTS Number Country Date 210,014 Great Britain Jan, 24, :1924467,860 Great Britain June 424;, 1937

